The invention is related generally to systems and methods for distributing RF signals and in particular to systems and methods for distributing one or more RF signals to plural receivers.
Modern communication systems often involve multiple antennas which feed RF signals to plural receivers. For example, as disclosed in co-pending application Ser. No.08/393,832 ("Frequency Switching Using RF Buss"), filed on the same day as the present application and of which this inventor is one of the co-inventors, in one telephone communication system, the RF signals from three antennas may be fed to many receivers so that various telephone conversations may be independently decoded and applied to a terrestrial telephone network. With reference to FIG. 1, in a prior art system, it is known to separately connect each feed from each of the antennas to each of the receivers. Such an arrangement provides all the required signals to the receivers so that the receivers may select any sub-signal from within the plural RF signals but at a cost of many power splitters and a large quantity of RF signal cabling. For example, in one proposed system, six antenna feed a rack of 96 receivers. In a conventional signal distribution system, 576 separate runs of coaxial cable and many power splitters would be required to distribute the signals to the receiver.
Considerable cost and complexity could be avoided if the RF signals could provided to plural receivers without the necessity of many splitters and massive cabling. It is known in the prior art to bus electrical signals among plural devices which communicate or interconnect via the bus. Busses, however, are generally not usable for RF signals because of the tendency of RF signals to exhibit standing waves and reflections resulting from mismatched impedance. The attachment of receiving or similar devices to an RF signal buss significantly alters the loading and impedance on the bus and may thereby adversely affect signal propagation on the bus.
It is also known in the prior art to distribute signals (including power, ground, and communications) to various devices in a rack or chassis of similar devices wherein the devices are contained on printed circuit boards which may be selectively attached to or removed from the rack as needed to handle the workload applied to the rack. In such racks, often a motherboard busses around various signals which are electrically connected to circuits on daughterboards when the daughterboards are physically (and removably) attached to the mother board of the rack or chassis. While such motherboard/daughterboard systems are common in many electrical systems, they are not generally found in RF signal distribution systems for the same reasons as given above. Additionally, if the number of daughterboards attached to the motherboard at one time is variable (i.e., the daughterboards may be removed or added as communications load change), the effects of the presence/absence of daughterboards on the RF bus may significantly degrade the RF signals being bussed.
Accordingly, it is an object of the present invention to provide a system and method which obviates these and other known difficulties in the prior art.
It is another object of the present invention to provide a novel system and method in which RF signals from one or more antennas can be provided to plural receivers without a requirement to separately connect each antenna feed to each receiver in a matched RF distribution fashion.
It is still another object of the present invention to provide a novel system and method in which RF signals may be bussed to one or more receiving devices where the number of receiving devices is not predetermined.
It is yet another object of the present invention to provide a novel system and method for attaching signal receiving devices to a RF signal bus.
It is a further object of the present invention to provide a novel system and method of interconnecting one or more daughterboards to a motherboard without substantially adversely affecting a RF signal being connected between the boards.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.